Proppant with polyurea-type coating

摘要

Proppants for hydraulic fracturing of oil and gas wells are coated with a polyurea-type coating. In a preferred embodiment, the polyurea-type coating is formed by contacting a polymeric isocyanate with an amount of water and a blowing catalyst at a rate and quantity sufficient to generate a reactive amine in situ on the outer surface of the proppant which thereby reacts with unconverted polymeric isocyanate to form a thin polyurea-type surface coating that is substantially solid and lacks foam or substantial porosity. Alternatively, the polyurea-type can be produced by selecting reactive amine compounds and isocyanates to develop the coated proppant. The coated proppants retain the discrete, free-flowing character of the original core solids but with the beneficial effects of the polyurea-type coating of the present invention.

主权项

1. A method for the production of proppant that is coated with a substantially cured, polyurea-type coating, the method comprising:
forming a thin, glassy film of said polyurea-type coating on a heated proppant core solid, having a size range of about 16 to about 100 mesh, by contacting said core simultaneously with: (a) an isocyanate comprising at least 2 reactive isocyanate groups; and (b) a mixture of water and a curing agent and/or catalyst in amounts sufficient to promote the formation of said thin, glass film, substantially cured, polyurea-type coating, wherein said water is contacted with said isocyanate at a rate sufficient to form a reactive amine that then reacts with additional isocyanate to form said polyurea-type coating on said proppant and wherein the proppant core solid, water and isocyanate are added a rate sufficient to maintain a proportion of 5-30 wt % water to 95-70% isocyanate, and wherein said coating exhibits an interparticle bond strength of at least 20 psi in unconfined compressive strength testing.